Treatment of 2-aminobenzothiazole (1) with chloroacetyl chloride in dry benzene gave N-(benzo[d]thiazol-2-yl)-2-chloroacetamide (3), which under reaction with potassium thiocyanate in refluxing acetone afforded 2-(benzo[d]thiazol-2-ylamino)thiaazol-4(5H)-one (4). 2- Benzothiazolylimino-5-(arylidene)thiazol-4(5H)-one derivatives (5a-m) were synthesized by reaction of (4) with appropriate aromatic aldehydes and assayed their antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Streptococcus group D, E. coli, Proteus vulgaris and Klebsiella pneumoniae strains. The antibacterial activity of these compounds revealed that the Bacillus subtilis was the most sensitive strain to 5a, 5c, 5d, 5g, and 5m compared to other investigated bacterial strains.